"Oathbreakers" are evil, by definition, "oathbreakers" are not. A oath of conquest paladin that broke their oath for good reasons, would be more suited for a oath of redemption.
then ur an oath of redemption get fucked dumbass, read the lore
The problem with Redemption is that it's an externally-focused oath, trying to redeem others. A conquest paladin having an "am I the baddy" moment and turning into a redemption paladin is like a douchy bully who suddenly finds Jesus then tries to convert people without apologizing for the years of bullying.
D&D needs an Oath of Atonement which would be specifically focused on making up for the shit you did as a previous less-than-moral paladin subclass (mostly conquest, sometimes revenge, occasionally crown or devotion).
All serious tho, one of ideas I know I will never be able to do is to play the same Paladin in 3 succesful campaigns in one setting, first as Oath of Conquest, then Oathbreaker, then Oath of Redemption. I first it's a better growth if there is a transition phase before adopting the Redeption.